1. Field of the Invention
This invention relates to power supplies, and more particularly to power supplies for solid state lighting systems.
2. Description of the Related Art
Light emitting diodes (LEDs) are a known class of solid state devices that convert electric energy to light. They generally comprise one or more active layers of semiconductor material sandwiched between oppositely doped layers. When a bias is applied across the doped layers, holes and electrons are injected into the active layer where they recombine to generate light. Light is emitted omnidirectionally from the active layer and from all surfaces of the LED. The useful light is generally emitted in the direction of the LED's top surface, which is usually p-type.
Developments in LED technology have resulted in devices that are brighter, more efficient and more reliable. LEDs are now being used in many different applications that were previously the realm of incandescent bulbs; some of these include architectural lighting, displays, pool/spa lighting, automobile taillights and traffic signals. As the efficiency of LEDs improves it is expected that they will be used in most lighting applications. These lighting systems are generally referred to as solid state lighting systems, and can also use other solid state lighting devices such as solid state lasers.
Some examples of solid state lighting systems are described in U.S. Pat. Nos. 6,776,504 and 6,969,179 both to Sloan et al., assigned to SloanLED, Inc. (assignee of present application), and both entitled “Perimeter Lighting Apparatus.” These systems generally comprise one or more elongated perimeter lights having a linear array of light sources (LEDs) that are electrically illuminated. The LEDs are disposed within an elongated transparent tube, with the tube transmitting and dispersing the light from the LEDs giving the appearance of a continuous light source. The array of LEDs can be cut at intervals down its length to shorten it and the light sources that remain in the array continue to emit light. The tube can also be cut to match the length of said array. The perimeter lights can also be electrically coupled in a daisy chain with the electrical power at each of the perimeter lights being transmitted to the successive light. A mechanism is included for anchoring the plurality of perimeter lights to a structure to illuminate it. Each of the perimeter lights can be cut at intervals down its length while not interfering with its ability to transmit its electrical power to successive lights.
Another example of an SSL system is described in U.S. Pat. No. 9,932,495 to Sloan et al., assigned to SloanLED, Inc., and entitled “Channel Letter Lighting Using Light Emitting Diodes.” These systems generally comprise a plurality of channel lighting units electrically connected to one another so that a power signal applied to the lighting system is transmitted to each of the plurality of lighting units. The units are mounted in channel letter typically having a housing in the shape of a letter. A translucent lens is included over the housing to transmit light from within the housing. A power signal applied to the first of the plurality of lighting units in the daisy chain is transmitted to the remaining of the plurality of lighting units to illuminate the channel letter.
These SSL systems are typically powered by a direct current (DC) power signal, with one example of such a signal being 12 volts DC. The power source (primary source) at many commercial and residential locations, however, is typically in the range of 100-240 volts alternating current (AC). As a result, a power supply is needed to convert the primary AC source to the appropriate DC source to drive the SSL systems. These power supplies are electrically connected to the primary source at a conventional junction box. The junction boxes have “knock-outs” to create a circular opening in the junction box for connecting wires to pass through. Connecting wires pass through the opening and are connected at one end within the junction box to the primary source. At the other end, the wires pass into the power supply and are connected to the conversion circuitry within the power supply. A conduit is usually mounted between the SSL system power supply and junction box, with the connecting wires passing through the conduit. The conduit is then connected at the ends to the solid state lighting system power supply and the junction box, with some embodiments having a watertight seal at the ends. This installation process can be complicated and cumbersome; particularly in those installations where more than one solid state lighting system power supply is connected to a junction box.